In traditional telecommunications networks, network usage auditing and policing are relatively easy to implement, because telecommunications signaling and media sessions each traverse a designated set of nodes controlled by the network operator. As used herein, the term “media session” refers to an association between end users that carries end user communications. The term “signaling session” refers to messages exchanged between end user and/or network devices to establish, tear down, or maintain a media session. Network usage auditing and policing can be achieved by monitoring the media and/or the signaling session at the nodes through which the messages travel. Auditing and fraud prevention in traditional telecommunications networks is further facilitated by the fact that such networks use time division multiplexed (TDM) channels to carry media and signaling sessions, where the bandwidth allocated to each channel is fixed, limiting the ability of users to exceed allocated bandwidth. For auditing in traditional telecommunications networks, signaling and media usage records can be collected directly from the end office switches to determine whether any irregularities exist.
In IP networks, such as voice over IP networks that use SIP for signaling, there is no guarantee that signaling or media sessions will traverse a predictable set of nodes managed by the network operator. In one example of media session fraud, end users can collude to send signaling that indicates to the network that a media session has been terminated but then continue media communications after sending the termination signaling. As a result, network resources may be used without authorization and charging for the call will not correspond to usage time indicated by the signaling. In other examples of media session fraud, end users can collude to use more bandwidth or a different codec than indicated in a signaling session used to establish the media session.
To alleviate some of these problems associated with usage auditing and fraud prevention in IP-based telecommunications networks, a SIP policy framework has been defined where a user agent client can communicate with the policy server to determine the media policy for a media session. However, the policy framework proposed in current Internet drafts does not specify a mechanism for enforcing the media portion of the policy in light of the above described problem of lack of path predictability for media streams. In other words, the policy framework specifies how the user agent client obtains a media policy from a policy server, but does not specify a mechanism for enforcing a media policy in light of the fact that real time transport protocol (RTP) media streams between user agent clients may traverse any set of nodes that can forward IP traffic. Because there is no guarantee that media traffic will traverse a given node or set of nodes, there is no centralized node or set of nodes to perform policy enforcement.
Media relays have been developed to allow user agent clients to communicate with each other through network address translators and firewalls. However, such media relays are typically contacted directly by the user agent clients and there is currently no communication between the media relays and SIP proxy or policy nodes.
Session border controllers provide a single location for signaling and policy enforcement. However, session border controllers are monolithic and are usually only located at boundaries between networks managed by different service providers. Accordingly, in light of these difficulties, there exists a long felt need for methods, systems, and computer readable media for media session policy auditing and enforcement using a media relay and session initiation protocol (SIP) signaling.